|
Limbless Vertebrate
Many vertebrates have evolved limbless, limb-reduced, or apodous forms. Reptiles have on a number of occasions evolved into limbless forms – snakes, amphisbaenia, and legless lizards (limb loss in lizards has evolved independently several times, examples include the families Pygopodidae and Dibamidae and species of ''Isopachys'', '' Anguis'', and ''Ophisaurus)''. The same is true of amphibians – caecilians, Sirenidae (a clade of salamanders that are limbless except for atrophied front limbs), Amphiumidae (a clade of salamander with extremely atrophied limbs that appear non-functional) and at least three extinct groups (Aïstopoda, Lysorophia, and Adelospondyli). Larval amphibians, tadpoles, are also often limbless. Legless forms of reptiles and amphibians probably evolved so as to be able to move underground or in water more easily. Some analyses suggest that elongation and undulatory locomotion (slithering) evolved first, before limb loss. The debate about the origin of lim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anguidae
Anguidae refers to a large and diverse family of lizards native to the Northern Hemisphere. Common characteristics of this group include a reduced supratemporal arch, striations on the medial faces of tooth crowns, osteoderms, and a lateral fold in the skin of most taxa. The group includes the slowworms, glass lizards, and alligator lizards, among others. The family is divided into two subfamilies (Anguinae and Gerrhonotinae), and contains about 87 species in 8 genera. Morphology and reproduction Anguids have hard osteoderms beneath their scales giving them an armored appearance. Many of the species have reduced or absent limbs, giving them a snake-like appearance, while others are fully limbed. Body type varies among species, with sizes ranging from 10 cm to 1.5 m. The group includes oviparous and viviparous species, both of which can be observed in a single genus at times. Feeding and habitat These lizards are known carnivorous or insectivorous foragers, feeding p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lysorophia
Lysorophia is an order of fossorial Carboniferous and Permian tetrapods within the Recumbirostra. Lysorophians resembled small snakes, as their bodies are extremely elongate. There is a single family, the Molgophidae (previously known as Lysorophidae). Currently there are around five genera included within Lysorophia, although many may not be valid. Description The skull is heavily built but with large lateral openings to accommodate jaw musculature, with small orbits restricted to the anterior edge of the large fenestrae. The intertemporal, supratemporal, postfrontal, and jugal bones of the skull have disappeared. The mandibles are short and robust with a small number of large triangular teeth. Although it was initially thought that the maxilla and premaxilla were freely movable, detailed anatomical studies show that this is not the case. The braincase is extremely robust, suggesting that lysorophians engaged in headfirst burrowing. The torso is very elongate, the limbs ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cetacea
Cetacea (; , ) is an infraorder of aquatic mammals that includes whales, dolphins, and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively carnivorous diet. They propel themselves through the water with powerful up-and-down movement of their tail which ends in a paddle-like fluke, using their flipper-shaped forelimbs to maneuver. While the majority of cetaceans live in marine environments, a small number exclusively reside in brackish water or fresh water. Having a cosmopolitan distribution, they can be found in some rivers and all of Earth's oceans, and many species inhabit vast ranges where they migrate with the changing of the seasons. Cetaceans are famous for their high intelligence and complex social behaviour as well as for the enormous size of some of the group's members, such as the blue whale which reaches a maximum confirmed length of 29.9 meters (98 feet) and a weight of 173 tonnes (190 short to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lamprey
Lampreys (sometimes inaccurately called lamprey eels) are an ancient extant lineage of jawless fish of the order Petromyzontiformes , placed in the superclass Cyclostomata. The adult lamprey may be characterized by a toothed, funnel-like sucking mouth. The common name "lamprey" is probably derived from Latin , which may mean "stone licker" ( "to lick" + "stone"), though the etymology is uncertain. ''Lamprey'' is sometimes seen for the plural form. There are about 38 known extant species of lampreys and five known extinct species. Parasitic carnivorous species are the most well-known, and feed by boring into the flesh of other fish to suck their blood; but only 18 species of lampreys engage in this micropredatory lifestyle. Of the 18 carnivorous species, nine migrate from saltwater to freshwater to breed (some of them also have freshwater populations), and nine live exclusively in freshwater. All non-carnivorous forms are freshwater species. Adults of the non-carnivorous ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hagfish
Hagfish, of the class Myxini (also known as Hyperotreti) and order Myxiniformes , are eel-shaped, slime-producing marine fish (occasionally called slime eels). They are the only known living animals that have a skull but no vertebral column, although hagfish do have rudimentary vertebrae. Along with lampreys, hagfish are jawless; the two form the sister group to jawed vertebrates, and living hagfish remain similar to hagfish from around 300 million years ago. The classification of hagfish had been controversial. The issue was whether the hagfish was a degenerate type of vertebrate-fish that through evolution had lost its vertebrae (the original scheme) and was most closely related to lampreys, or whether hagfish represent a stage that precedes the evolution of the vertebral column (the alternative scheme) as is the case with lancelets. Recent DNA evidence has supported the original scheme. The original scheme groups hagfish and lampreys together as cyclostomes (or historicall ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Swamp Eel
The swamp eels (also written "swamp-eels") are a family (Synbranchidae) of freshwater eel-like fishes of the tropics and subtropics. Most species are able to breathe air and typically live in marshes, ponds and damp places, sometimes burying themselves in the mud if the water source dries up. They have various adaptations to suit this lifestyle; they are long and slender, they lack pectoral and pelvic fins, and their dorsal and anal fins are vestigial, making them limbless vertebrates. They lack scales and a swimbladder, and their gills open on the throat in a slit or pore. Oxygen can be absorbed through the lining of the mouth and pharynx, which is rich in blood vessels and acts as a "lung". Although adult swamp eels have virtually no fins, the larvae have large pectoral fins which they use to fan water over their bodies, thus ensuring gas exchange before their adult breathing apparatus develops. When about a fortnight old they shed these fins and assume the adult form. Most spec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Typhlops
''Typhlops'' is a genus of blind snakes in the family Typhlopidae. The genus is endemic to the West Indies. Some species which were formerly placed in the genus ''Typhlops'' have been moved to the genera '' Afrotyphlops, Amerotyphlops, Anilios, Antillotyphlops, Argyrophis, Cubatyphlops, Indotyphlops, Letheobia, Madatyphlops, Malayotyphlops'', and ''Xerotyphlops''. Species ''*) Not including the nominate subspecies.'' ) Type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen .... References External links * Further reading * Hedges SB, Marion AB, Lipp KM, Marin J, Vidal N (2014). "A taxonomic framework for typhlopid snakes from the Caribbean and other regions (Reptilia, Squamata)". ''Caribbean Herpetology'' 49: 1-61. (''Amerotyphlops, Antillotyphlops, Asiatyphlops, C ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pythonidae
The Pythonidae, commonly known as pythons, are a family of nonvenomous snakes found in Africa, Asia, and Australia. Among its members are some of the largest snakes in the world. Ten genera and 42 species are currently recognized. Distribution and habitat Pythons are found in sub-Saharan Africa, Nepal, India, Bangladesh, Sri Lanka, Southeast Asia, southeastern Pakistan, southern China, the Philippines and Australia. In the United States, an introduced population of Burmese pythons, ''Python bivittatus'', has existed as an invasive species in the Everglades National Park since the late 1990s. Common names * Sinhala - පිඹුරා (''Pimbura'') *Telugu - కొండచిలువ (Kondachiluva) * Odia - ଅଜଗର (Ajagara) *Malayalam - പെരുമ്പാമ്പ് (perumpāmp) *Hindi - अजगर ('Ajgar') Conservation Many species have been hunted aggressively, which has greatly reduced the population of some, such as the Indian python, ''Python molu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Boa Constrictor
The boa constrictor (scientific name also ''Boa constrictor''), also called the red-tailed boa, is a species of large, non-venomous, heavy-bodied snake that is frequently kept and bred in captivity. The boa constrictor is a member of the family Boidae, found in tropical South America, as well as some islands in the Caribbean. A staple of private collections and public displays, its color pattern is highly variable yet distinctive. Four subspecies are currently recognized. This article focuses on the species ''Boa constrictor'' as a whole, and on the nominate subspecies ''B. c. constrictor''. Common names Though all boids are constrictors, only this species is properly referred to as a "boa constrictor"—a rare instance of an animal having the same common English name and scientific binomial name. All subspecies are referred to as "boa constrictors", and are part of a diverse group of New World boas referred to as "red-tailed" boas, comprising species of both ''Boa constrictor' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pelvic Spur
Pelvic spurs are the externally visible portion of the vestigial remnants of legs found on each side of the cloaca in primitive snakes, such as boas and pythons. The remnants of a pelvis and femur, which have no connection with the spine, simply "float" in the muscle mass. The femur protrudes from the snake's body and is covered by a horny structure, which resembles a spur or claw. Males' spurs are generally longer and more pointed than females', and are used for clasping and tickling during courtship and mating In biology, mating is the pairing of either opposite-sex or hermaphroditic organisms for the purposes of sexual reproduction. ''Fertilization'' is the fusion of two gametes. ''Copulation'' is the union of the sex organs of two sexually reproduc ..., as well as combat with other males in some species. These spurs represent a sexually dimorphic feature, and for some species, spurs can reliably be used to identify the sex of a snake. References Snake anatomy { ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phlegethontia
''Phlegethontia'' is an extinct genus of aïstopod stegocephalians from the Carboniferous and Permian periods of Europe and North America. It was about long, and possessed a lightly built skull with many openings, unlike some earlier relatives. ''"Dolichosoma" longissima'', named by Antonin Fritsch in 1875, has been reassigned to the genus ''Phlegethontia'' and is now considered to be ''P. longissima''. ''"Dolichosoma"'' has been considered to be a ''nomen nudum'' because the holotype was inadequately described through a layer of matrix by Thomas Henry Huxley Thomas Henry Huxley (4 May 1825 – 29 June 1895) was an English biologist and anthropologist specialising in comparative anatomy. He has become known as "Darwin's Bulldog" for his advocacy of Charles Darwin's theory of evolution. The storie ... in 1867. References External linksFossil picture. Aistopods Carboniferous fish of Europe Carboniferous fish of North America Permian fish of Europe Permian fis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Undulatory Locomotion
Undulatory locomotion is the type of motion characterized by wave-like movement patterns that act to propel an animal forward. Examples of this type of gait include crawling in snakes, or swimming in the lamprey. Although this is typically the type of gait utilized by limbless animals, some creatures with limbs, such as the salamander, forgo use of their legs in certain environments and exhibit undulatory locomotion. In robotics this movement strategy is studied in order to create novel robotic devices capable of traversing a variety of environments. Environmental interactions In limbless locomotion, forward locomotion is generated by propagating flexural waves along the length of the animal's body. Forces generated between the animal and surrounding environment lead to a generation of alternating sideways forces that act to move the animal forward. These forces generate thrust and drag. Hydrodynamics Simulation predicts that thrust and drag are dominated by viscous forces a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
